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Saturday, March 26, 2011

We’re losing our nights


Light pollution has always been the bane of stargazers. A new study by Christopher Kbya and his team from the Institute for Space Sciences and the Leibniz-Institute shows just how pervasive this problem has become. According to them, on a cloudy day in Berlin the sky is ten times brighter than it would be without the anthropomorphic light sources.


Berlin at night

Photo: C Kyba.

Historically, astronomers have only measured the amount of light pollution on cloudless nights since they don’t tend to use their light telescopes on cloudy nights. And light pollution is a problem even on clear nights. However, as clouds serve to redirect light back in the direction from whence it came, the problem can be magnified many times on cloudy nights. This isn’t so much a problem for astronomers, again, they aren’t looking at the sky on cloudy nights anyway. It could be a huge problem for the plants and animals that rely on the absence of light to trigger their reproductive and behavioral cycles.

I should add that all the light measurements were taken on moonless nights, and yet the amount of light in the urban settings was comparable to that of a full moon in a rural setting. Many organisms have not only day/night cycles but also monthly rhythms that depend on the lunar stages, especially the times of full or new moons. Although the authors did not test this directly, it’s easy to assume that such creatures would be seriously disoriented by the light pollution coming from our cities.

If you want to help astronomers assess the amount of light pollution in your area, you can participate in the Globe at Night project. Phil Plait has more information about this on his Bad Astronomy blog.